文件名称：GifDecoder
文件大小：17KB
文件格式：JAVA
更新时间：2022-03-28 06:57:01
java
package org.hds.Graphics; import java.net.*; import java.io.*; import java.util.*; import java.awt.*; import java.awt.image.*; public class GifDecoder { /** * File read status: No errors. */ public static final int STATUS_OK = 0; /** * File read status: Error decoding file (may be partially decoded) */ public static final int STATUS_FORMAT_ERROR = 1; /** * File read status: Unable to open source. */ public static final int STATUS_OPEN_ERROR = 2; protected BufferedInputStream in; protected int status; protected int width; // full image width protected int height; // full image height protected boolean gctFlag; // global color table used protected int gctSize; // size of global color table protected int loopCount = 1; // iterations; 0 = repeat forever protected int[] gct; // global color table protected int[] lct; // local color table protected int[] act; // active color table protected int bgIndex; // background color index protected int bgColor; // background color protected int lastBgColor; // previous bg color protected int pixelAspect; // pixel aspect ratio protected boolean lctFlag; // local color table flag protected boolean interlace; // interlace flag protected int lctSize; // local color table size protected int ix, iy, iw, ih; // current image rectangle protected Rectangle lastRect; // last image rect protected BufferedImage image; // current frame protected BufferedImage lastImage; // previous frame protected byte[] block = new byte[256]; // current data block protected int blockSize = 0; // block size // last graphic control extension info protected int dispose = 0; // 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev protected int lastDispose = 0; protected boolean transparency = false; // use transparent color protected int delay = 0; // delay in milliseconds protected int totaldelay = 0; // delay in milliseconds protected int transIndex; // transparent color index protected static final int MaxStackSize = 4096; // max decoder pixel stack size // LZW decoder working arrays protected short[] prefix; protected byte[] suffix; protected byte[] pixelStack; protected byte[] pixels; protected ArrayList frames; // frames read from current file protected int frameCount; static class GifFrame { public GifFrame(BufferedImage im, int del) { image = im; delay = del; } public BufferedImage image; public int delay; } /** * Gets display duration for specified frame. * * @param n int index of frame * @return delay in milliseconds */ public int getDelay(int n) { // delay = -1; if ((n >= 0) && (n < frameCount)) { delay = ((GifFrame) frames.get(n)).delay; } return delay; } /** * Gets the number of frames read from file. * @return frame count */ public int getFrameCount() { return frameCount; } /** * Gets the number of frames read from file. * @return frame count */ public int gettotaldelay() { return totaldelay; } /** * Gets the first (or only) image read. * * @return BufferedImage containing first frame, or null if none. */ public BufferedImage getImage() { return getFrame(0); } /** * Gets the "Netscape" iteration count, if any. * A count of 0 means repeat indefinitiely. * * @return iteration count if one was specified, else 1. */ public int getLoopCount() { return loopCount; } /** * Creates new frame image from current data (and previous * frames as specified by their disposition codes). */ protected void setPixels() { // expose destination image's pixels as int array int[] dest = ((DataBufferInt) image.getRaster().getDataBuffer()).getData(); // fill in starting image contents based on last image's dispose code if (lastDispose > 0) { if (lastDispose == 3) { // use image before last int n = frameCount - 2; if (n > 0) { lastImage = getFrame(n - 1); } else { lastImage = null; } } if (lastImage != null) { int[] prev = ((DataBufferInt) lastImage.getRaster().getDataBuffer()).getData(); System.arraycopy(prev, 0, dest, 0, width * height); // copy pixels if (lastDispose == 2) { // fill last image rect area with background color Graphics2D g = image.createGraphics(); Color c = null; if (transparency) { c = new Color(0, 0, 0, 0); // assume background is transparent } else { c = new Color(lastBgColor); // use given background color } g.setColor(c); g.setComposite(AlphaComposite.Src); // replace area g.fill(lastRect); g.dispose(); } } } // copy each source line to the appropriate place in the destination int pass = 1; int inc = 8; int iline = 0; for (int i = 0; i < ih; i++) { int line = i; if (interlace) { if (iline >= ih) { pass++; switch (pass) { case 2 : iline = 4; break; case 3 : iline = 2; inc = 4; break; case 4 : iline = 1; inc = 2; } } line = iline; iline += inc; } line += iy; if (line < height) { int k = line * width; int dx = k + ix; // start of line in dest int dlim = dx + iw; // end of dest line if ((k + width) < dlim) { dlim = k + width; // past dest edge } int sx = i * iw; // start of line in source while (dx < dlim) { // map color and insert in destination int index = ((int) pixels[sx++]) & 0xff; int c = act[index]; if (c != 0) { dest[dx] = c; } dx++; } } } } /** * Gets the image contents of frame n. * * @return BufferedImage representation of frame, or null if n is invalid. */ public BufferedImage getFrame(int n) { BufferedImage im = null; if ((n >= 0) && (n < frameCount)) { im = ((GifFrame) frames.get(n)).image; } return im; } /** * Gets image size. * * @return GIF image dimensions */ public Dimension getFrameSize() { return new Dimension(width, height); } /** * Reads GIF image from stream * * @param BufferedInputStream containing GIF file. * @return read status code (0 = no errors) */ public int read(BufferedInputStream is) { init(); if (is != null) { in = is; readHeader(); if (!err()) { readContents(); if (frameCount < 0) { status = STATUS_FORMAT_ERROR; } } } else { status = STATUS_OPEN_ERROR; } try { is.close(); } catch (IOException e) { } return status; } /** * Reads GIF image from stream * * @param InputStream containing GIF file. * @return read status code (0 = no errors) */ public int read(InputStream is) { init(); if (is != null) { if (!(is instanceof BufferedInputStream)) is = new BufferedInputStream(is); in = (BufferedInputStream) is; readHeader(); if (!err()) { readContents(); if (frameCount < 0) { status = STATUS_FORMAT_ERROR; } } } else { status = STATUS_OPEN_ERROR; } try { is.close(); } catch (IOException e) { } return status; } /** * Reads GIF file from specified file/URL source * (URL assumed if name contains ":/" or "file:") * * @param name String containing source * @return read status code (0 = no errors) */ public int read(String name) { status = STATUS_OK; try { name = name.trim().toLowerCase(); if ((name.indexOf("file:") >= 0) || (name.indexOf(":/") > 0)) { URL url = new URL(name); in = new BufferedInputStream(url.openStream()); } else { in = new BufferedInputStream(new FileInputStream(name)); } status = read(in); } catch (IOException e) { status = STATUS_OPEN_ERROR; } return status; } /** * Decodes LZW image data into pixel array. * Adapted from John Cristy's ImageMagick. */ protected void decodeImageData() { int NullCode = -1; int npix = iw * ih; int available, clear, code_mask, code_size, end_of_information, in_code, old_code, bits, code, count, i, datum, data_size, first, top, bi, pi; if ((pixels == null) || (pixels.length < npix)) { pixels = new byte[npix]; // allocate new pixel array } if (prefix == null) prefix = new short[MaxStackSize]; if (suffix == null) suffix = new byte[MaxStackSize]; if (pixelStack == null) pixelStack = new byte[MaxStackSize + 1]; // Initialize GIF data stream decoder. data_size = read(); clear = 1 << data_size; end_of_information = clear + 1; available = clear + 2; old_code = NullCode; code_size = data_size + 1; code_mask = (1 << code_size) - 1; for (code = 0; code < clear; code++) { prefix[code] = 0; suffix[code] = (byte) code; } // Decode GIF pixel stream. datum = bits = count = first = top = pi = bi = 0; for (i = 0; i < npix;) { if (top == 0) { if (bits < code_size) { // Load bytes until there are enough bits for a code. if (count == 0) { // Read a new data block. count = readBlock(); if (count <= 0) break; bi = 0; } datum += (((int) block[bi]) & 0xff) << bits; bits += 8; bi++; count--; continue; } // Get the next code. code = datum & code_mask; datum >>= code_size; bits -= code_size; // Interpret the code if ((code > available) || (code == end_of_information)) break; if (code == clear) { // Reset decoder. code_size = data_size + 1; code_mask = (1 << code_size) - 1; available = clear + 2; old_code = NullCode; continue; } if (old_code == NullCode) { pixelStack[top++] = suffix[code]; old_code = code; first = code; continue; } in_code = code; if (code == available) { pixelStack[top++] = (byte) first; code = old_code; } while (code > clear) { pixelStack[top++] = suffix[code]; code = prefix[code]; } first = ((int) suffix[code]) & 0xff; // Add a new string to the string table, if (available >= MaxStackSize) break; pixelStack[top++] = (byte) first; prefix[available] = (short) old_code; suffix[available] = (byte) first; available++; if (((available & code_mask) == 0) && (available < MaxStackSize)) { code_size++; code_mask += available; } old_code = in_code; } // Pop a pixel off the pixel stack. top--; pixels[pi++] = pixelStack[top]; i++; } for (i = pi; i < npix; i++) { pixels[i] = 0; // clear missing pixels } } /** * Returns true if an error was encountered during reading/decoding */ protected boolean err() { return status != STATUS_OK; } /** * Initializes or re-initializes reader */ protected void init() { status = STATUS_OK; frameCount = 0; frames = new ArrayList(); gct = null; lct = null; } /** * Reads a single byte from the input stream. */ protected int read() { int curByte = 0; try { curByte = in.read(); } catch (IOException e) { status = STATUS_FORMAT_ERROR; } return curByte; } /** * Reads next variable length block from input. * * @return number of bytes stored in "buffer" */ protected int readBlock() { blockSize = read(); int n = 0; if (blockSize > 0) { try { int count = 0; while (n < blockSize) { count = in.read(block, n, blockSize - n); if (count == -1) break; n += count; } } catch (IOException e) { } if (n < blockSize) { status = STATUS_FORMAT_ERROR; } } return n; } /** * Reads color table as 256 RGB integer values * * @param ncolors int number of colors to read * @return int array containing 256 colors (packed ARGB with full alpha) */ protected int[] readColorTable(int ncolors) { int nbytes = 3 * ncolors; int[] tab = null; byte[] c = new byte[nbytes]; int n = 0; try { n = in.read(c); } catch (IOException e) { } if (n < nbytes) { status = STATUS_FORMAT_ERROR; } else { tab = new int[256]; // max size to avoid bounds checks int i = 0; int j = 0; while (i < ncolors) { int r = ((int) c[j++]) & 0xff; int g = ((int) c[j++]) & 0xff; int b = ((int) c[j++]) & 0xff; tab[i++] = 0xff000000 | (r << 16) | (g << 8) | b; } } return tab; } /** * Main file parser. Reads GIF content blocks. */ protected void readContents() { // read GIF file content blocks boolean done = false; while (!(done || err())) { int code = read(); switch (code) { case 0x2C : // image separator readImage(); break; case 0x21 : // extension code = read(); switch (code) { case 0xf9 : // graphics control extension readGraphicControlExt(); break; case 0xff : // application extension readBlock(); String app = ""; for (int i = 0; i < 11; i++) { app += (char) block[i]; } if (app.equals("NETSCAPE2.0")) { readNetscapeExt(); } else skip(); // don't care break; default : // uninteresting extension skip(); } break; case 0x3b : // terminator done = true; break; case 0x00 : // bad byte, but keep going and see what happens break; default : status = STATUS_FORMAT_ERROR; } } } /** * Reads Graphics Control Extension values */ protected void readGraphicControlExt() { read(); // block size int packed = read(); // packed fields dispose = (packed & 0x1c) >> 2; // disposal method if (dispose == 0) { dispose = 1; // elect to keep old image if discretionary } transparency = (packed & 1) != 0; delay = readShort() * 10; // delay in milliseconds transIndex = read(); // transparent color index read(); // block terminator } /** * Reads GIF file header information. */ protected void readHeader() { String id = ""; for (int i = 0; i < 6; i++) { id += (char) read(); } /* * 如果id!=GIF89a佳毅判断不了暂时不用 */ if(!id.equals("GIF89a")) { status = STATUS_FORMAT_ERROR; return; } if (!id.startsWith("GIF")) { status = STATUS_FORMAT_ERROR; return; } readLSD(); if (gctFlag && !err()) {//全局定义颜色列表 gct = readColorTable(gctSize); bgColor = gct[bgIndex]; } } /** * Reads next frame image * 读每帧图片信息 */ protected void readImage() { ix = readShort(); // (sub)image position & size iy = readShort(); iw = readShort(); ih = readShort(); if(ix > width || iy > height || iw > width || ih > height)//当帧位置大小有问题佳毅不支持 {status = STATUS_FORMAT_ERROR;} int packed = read(); lctFlag = (packed & 0x80) != 0; // 1 - local color table flag局部颜色列表 interlace = (packed & 0x40) != 0; // 2 - interlace flag // 3 - sort flag // 4-5 - reserved lctSize = 2 << (packed & 7); // 6-8 - local color table size if (lctFlag) { status = STATUS_FORMAT_ERROR;//局部颜色列表 佳毅不支持 lct = readColorTable(lctSize); // read table act = lct; // make local table active } else { act = gct; // make global table active if (bgIndex == transIndex) bgColor = 0; } int save = 0; if (transparency) { save = act[transIndex]; act[transIndex] = 0; // set transparent color if specified } if (act == null) { status = STATUS_FORMAT_ERROR; // no color table defined } if (err()) return; decodeImageData(); // decode pixel data skip(); if (err()) return; frameCount++; // create new image to receive frame data image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB_PRE); setPixels(); // transfer pixel data to image frames.add(new GifFrame(image, delay)); // add image to frame list totaldelay += delay; if (transparency) { act[transIndex] = save; } resetFrame(); } /** * Reads Logical Screen Descriptor */ protected void readLSD() { // logical screen size width = readShort(); height = readShort(); // packed fields int packed = read(); gctFlag = (packed & 0x80) != 0; // 1 : global color table flag 全局定义颜色列表 true // 2-4 : color resolution // 5 : gct sort flag gctSize = 2 << (packed & 7); // 6-8 : gct size bgIndex = read(); // background color index pixelAspect = read(); // pixel aspect ratio } /** * Reads Netscape extenstion to obtain iteration count */ protected void readNetscapeExt() { do { readBlock(); if (block[0] == 1) { // loop count sub-block int b1 = ((int) block[1]) & 0xff; int b2 = ((int) block[2]) & 0xff; loopCount = (b2 << 8) | b1; } } while ((blockSize > 0) && !err()); } /** * Reads next 16-bit value, LSB first */ protected int readShort() { // read 16-bit value, LSB first return read() | (read() << 8); } /** * Resets frame state for reading next image. */ protected void resetFrame() { lastDispose = dispose; lastRect = new Rectangle(ix, iy, iw, ih); lastImage = image; lastBgColor = bgColor; int dispose = 0; boolean transparency = false; int delay = 0; lct = null; } protected void skip() { do { readBlock(); } while ((blockSize > 0) && !err()); } }